An illumination optical unit of the type set forth at the outset is known from DE 10 2008 001 511 A1, DE 10 2007 047 446 A1, US 2011/0001947 A1, WO 2009/132 756 A1, WO 2009/100 856 A1, and also U.S. Pat. Nos. 6,438,199 B1 and 6,658,084 B2.